Recent progress in flow‐induced polymer crystallization

Abstract

During industrial processing, such as film blowing and injection molding, semicrystalline polymers have to be subjected to external flow. Flow changes the nucleation rate, crystal morphology and polymorphism of polymers. As flow can be tunable, polymeric products with different macroscopic performance and versatile applications can be obtained. Understanding polymer crystallization with the presence of flow, or namely flow-induced crystallization (FIC), is crucial to optimize polymer processing parameters and to understand phase transition under far-from equilibrium conditions, as FIC is essentially a typical nonequilibrium process. Current review aims to summarizes recent achievements of FIC during last five years from three aspects: theory, experiment and simulation. First, we present the FIC model and theory, including the classical conformational entropy reduction model, the newly developed POLYdisperse STRain Accelerated Nucleation Dynamics (PolySTRAND) Model and uFIC Model. Then we discuss the FIC experiments under both well-controlled flow and complex processing conditions. Finally, we show the recent advance of FIC in computer simulation. With the fast development in modeling efficiency, more detailed nucleation and structure transition processes during FIC can be obtained, which promote the study of molecular mechanisms of FIC.

Optimum processing conditions for the maximum crystallization rate of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)

“…To date, PHBHHx has been used in various applications such as shopping bags, cutlery, straws, and food packaging 17,18 . To further extend the applicability of PHBHHx, it is necessary to increase its crystallization rate to reduce the cycle time and/or increase the production rate [19][20][21][22][23] . Therefore, considering actual processing operations, the crystallization behavior of a PHBHHx with various thermal and shear histories was examined in this study.Up to now, there have been a number of studies on the crystallization behavior of PHB and its copolymers.…”

Evolution of the Deformation‐ and Flow‐Induced Crystallization and Characterization of the Microstructure of a Single Spherulite, Lamella, and Chain of Isotactic Polypropylene

“…The dense domains are precursors for crystallization that may follow the spinodal decomposition-like process to initiate nucleation. [31][32][33][34][35][36] The ordered chain segments parallel interaction introduces the dense domains. [37][38][39] When the segmental chain lengths exceed the critical value of the persistence length (estimated to be about 2.38 nm), dense domains are formed.…”

Effect of Temperature on Flow-Induced Crystallization of Isotactic Polypropylene: A Molecular-Dynamics Study

“…Normally, crystallization has been characterized as a multistep process. 17 As far back as in the late 1990s, density fluctuations prior to crystallization under quiescent conditions were reported, 18,19 while later research 20,21 showed evidence that a mesomorphic structure precedes the well-defined lamellar crystal. Even if the exact structure of the mesophase still remains an open question, progress has been made toward understanding the different stages of the formation of such precursor.…”

“…In order to be able to tailor the final properties of the film, the intermediate stages of crystallization should be well-known. Normally, crystallization has been characterized as a multistep process . As far back as in the late 1990s, density fluctuations prior to crystallization under quiescent conditions were reported, , while later research , showed evidence that a mesomorphic structure precedes the well-defined lamellar crystal.…”